Cooperative Extension: Maine Wild Blueberries

6.10.15 Botrytis Infection Risk, June 8 to June 10

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With the wet weather over the past few days, we have had low to high risk of Botrytis infection in fields which already had Botrytis present.  If there was no Botrytis seen before this weekend in your field, it is unlikely there will be more disease now.  Most fields in the midcoast, Knox, Lincoln and Waldo counties, are past bloom and we have seen only low levels of Botrytis in some fields. Fields with no open flowers left are unlikely to experience Botrytis infection. Leaf infections by Botrytis can occur but are very patchy and usually occur in dense canopies with heavy flower infection on those plants that start the infection in the leaves. I have not seen it very often in our fields.

The cool weather during the last rain periods from Monday through Wednesday morning again kept the risk of Botrytis infection low in comparison to the number of hours the plants were wet.    Fungicide applications for Botrytis can only protect plants against infection and do not cure infections already present.

If your plants are finished blooming or close to finishing, there is no point in applying fungicides for Botrytis at this stage.  There is scattered rain showers forecast from Wednesday night through this weekend.  Fungicide applications will only be worthwhile if you have visible Botrytis infections already in your field, lots of blooms left, and a high likelihood of long periods of rain in the next few days in your area.